The electronic structure of InGaN epitaxial layers grown on sapphire substrates was studied using X-ray absorption at the In L3 and N K edges, as well as N Kα X-ray emission. Knowing that the InGaN crystallizes in an anisotropic wurtzite structure, the linear polarization of synchrotron radiation was exploited to estimate the influence of the crystal structure anisotropy on the distribution of the local density of states at the site of In and N. The calculated partial density of states describes the observed anisotropy in the measured spectra. Influence of the core–hole effect on the analyzed absorption spectra was verified and reveal that a core hole potential is effectively screened by the surface mobile electrons for the sample with maximum indium content. The bandgap values were provided for the investigated InGaN alloys and were found to vary preudo-lineary with indium content.

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